[Leetcode] Implement Trie (Prefix Tree)

Well, I just finished the week 1 of Algorithms on Strings. I think without doing homework problem there, I would not be able to think of how to represent the tree. BUT, of course, graph, adjacency list.

Implement a trie with insert, search, and startsWith methods.

class Trie(object):

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.tree = {}
        self.tree[0] = {}
        self.new_node_idx = 1

    def insert(self, word):
        """
        Inserts a word into the trie.
        :type word: str
        :rtype: void
        """
        current_node = 0
        word = word + '$'
        for i in range(len(word)):
            current_symbol = word[i]
            if current_symbol in self.tree[current_node]:
                current_node = self.tree[current_node][current_symbol]
            else:
                self.tree[current_node][current_symbol] = self.new_node_idx
                self.tree[self.new_node_idx] = {}
                current_node = self.new_node_idx
                self.new_node_idx += 1

    def search(self, word):
        """
        Returns if the word is in the trie.
        :type word: str
        :rtype: bool
        """
        word = word + '$'
        current_node = 0
        for i in range(len(word)):
            current_symbol = word[i]
            if current_symbol in self.tree[current_node]:
                current_node = self.tree[current_node][current_symbol]
            else:
                return False
        return True
    
    def startsWith(self, prefix):
        """
        Returns if there is any word in the trie that starts with the given prefix.
        :type prefix: str
        :rtype: bool
        """
        current_node = 0
        for i in range(len(prefix)):
            cur_symbol = prefix[i]
            if cur_symbol in self.tree[current_node]:
                current_node = self.tree[current_node][cur_symbol]
            else:
                return False
        return True

# Your Trie object will be instantiated and called as such:
# obj = Trie()
# obj.insert(word)
# param_2 = obj.search(word)
# param_3 = obj.startsWith(prefix)